Responded to a local Freecycle offer of a broken 50" Panasonic Viera plasma set (Model TH-50PZ850U), and hauled the beast home. Even got the remote with it! After setting it up on my dining room table (too big for the workbench in the shop!), I tried powering it up, and all that I get is a brief powerup (long enough to start the fans spinning), then shutdown and a repeated double blink from the power LED.
Suspecting that this was some kind of fault code, I did some Googling and found a service manual via ElectroTanya, and it turns out that the double blink indicates a problem with the +15V power rail. I also came across a LOT of folks with the exact same problem!
Following a suggestion I found on the AVS forums, I shot some freeze mist onto a little sub-module of the main "P" power board and tried starting the set again. Sure enough, It came right up!
There are 2 of the identical sub modules on the PCB (MC201 and MC301), and apparently these are a common enough failure point that there are ready-made repair kits to rebuild them, and a few folks offering rebuild services for these. Ordered a kit from a seller on eBay for ~$10 including shipping. The kit contains 2 SMPS controller ICs (NXP semiconductor TEA1611T) and 2 tiny (0602) ceramic 1 uF SMD caps. Playing around with my set and localizing the freeze mist a bit shows that it is actually the cap causing the issue in my set. Tacking in a regular leaded cap has the set working until the proper parts arrive in a couple days.
So it looks like I will have a nice "new" plasma set for the living room for $10 and a couple hours effort!